The present invention provides medical implants having a noncrystalline, high hardness, low friction, antimicrobial coating which is relatively well-tolerated by the body, and a process for preparing such coatings.
A common cause of failure of implanted biomedical devices is infection. The attachment of bacteria to medical implants and in-dwelling catheters, and the proliferation of such bacteria, is a major cause of infection during or after the implantation process. Treating an implant with antibiotics has not proven very effective to combat infections, and has sometimes resulted in the development of resistant strains of bacteria.
Silver coatings are effective to combat infections; however, silver coatings tend to cause tissue irritation, largely due to excessively rapid release of the silver into the surrounding tissues.
An antimicrobial coating for a medical implant is needed which has hardness and low friction properties, and that will result in a slow, long-term release of antimicrobial metal, atoms into the body in order to prevent infection.
The present invention provides a process of forming an antimicrobial coating on the surface of a medical implant comprising the steps of: placing the medical implant in a vacuum chamber evacuated to a pressure of less than about 10xe2x88x925 torr; depositing metal atoms, preferably silver atoms, onto the surface of the medical implant in an amount sufficient to impart antimicrobial protection to the medical implant; directing a vaporized stream of hydrocarbon precursor molecules toward the surface of the medical implant under temperature conditions sufficient to condense the hydrocarbon precursor molecules onto the surface of the implant, thereby forming a precursor film; and, bombarding the precursor film with an energetic beam of ions at a first energy, a first rate of ion arrival, and for a first amount of time sufficient to form on said surface a non-crystalline, amorphous carbonaceous coating containing an antimicrobially effective amount of said metal atoms. In an alternate embodiment, the metal is deposited onto the surface of the implant via an organo-metallic compound, which is used as the precursor material for the carbonaceous coating.